Aluminous abrasive and method of making the same



Patented Sept. 11,1923.

HAROLD A, RICHMOND AND ROBERT MACDONALD, JR., F NIAGARA FALLS, NEW

YORK, ASSIGNORS T0 GENERAL ABRASIVE COMPANY, INC OF NIAG NEW YORK, A CORPORATION OF NEW YORK.

ALUMINOUS ABRASIVE AND METHOD OF MAKING- THE SAME.

No Drawing.

To all whoma't may concern:

Be it known that we, HAROLD A. R1011- MOND and ROBERT MACDONALD, Jr., citizens of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have jointly invented a new and useful Improvement in Aluminou's Abrasives and Methods of Making the Same, of which the following is a specification.

Artificial aluminous abrasives have heretofore been made by melting bauxite or emery and reducing the impurities by means of carbon. Bauxite and emery each contain about 3% titanic anhydride and various percentages of silica and iron oxide. In the process of reduction most of the iron oxide and silica and part of the titanic anhydride are reduced to the metallic form and unite to produce impure ferrosilicon. Whenthe molten alumina cools it crystallizes. The ferrosilicon is separated from the crystalline alumina by hand picking, by magnets, or otherwise. A representative analysis of artificial corundum prepare-d in this manner is as follows:

A10 95.3% at. 1. 8% Fe O 8% Tie, 2.1%

Artificial corundum like that described above is suitable for certain grinding and polishing operations. But we have found that" for the highest efliciency on many op erations artificial corundum having greater resistance to fracture must be used, and that there must be a certain relation between the resistance to fracture of the abrasive and the toughness of the material which is being ground. The reason for this is that, the tougher the material that is being ground, the greater is the shattering effect-0n the abrasive grains. 'Thus 'a steel forging will have a greater tendency to fracture the abrasive grains of a grinding wheel than will a $5 piece of cast iron. The grains used in a grinding wheel for the former class of work should therefore possess greater resistance 'to fracture than those in -a wheel for the latter purpose. If the grains fracture too easily. they will shatter beforethey have accomplished sufiicient work, and the durability of the grinding orpolishing wheel will be lessened. q'Qn theother hand, if the frac- Applicatlon filed April 25, 1922. Serial No. 556,538.

ture resistance of the grains is too great for the particular class of work on which they are used, their points or cutting edges will become dulled before the grains.fracture and thegrinding or polishing wheel will lose a part of its free cutting qualities. In this case the grains inay be torn bodily from the surface of the wheel and wasted. Toobtain the best results the fracture resistance of the grains must be nicely adjusted to the f toughness of the material being ground. To accomplish this adjustment a practicable means must be provided for controlling the fracture resistance of the abrasive.

We have discovered that the resistance to fracture of artificial'corundum varies, other the average resistance to fracture of each to be as indicated below, the grains tested in each case measuringlone-tenth of an inch across;

Titanic anhydrlde. Pressurerequired to crash.

I 2% 'lbs. 3% 66 lbs. 4% 74 lbs.- 5% 79 lbs. 6% Q 82 lbs.

- ment consists inincreasing and regulating the percentage of titanic anh'ydride while maintaining appreciable quantities of bothsilica and iron oxide in the product.

A distinction should be drawn between the resistance to fracture of an abrasive and its hardness. An abrasive may be exceedingly hard, and at the same time so friable that the crystals may be readily broken. This is the case with silicon carbide abrasive.- A.

change in the fracture; resistance of an abrasive does not necessarily have any effect on its hardness. The method we have or other reducing agent required will depend in the crystalline alumina. chips or iron in other form is also added,

finished product. We have found that approximately one-third' of the ore will be reduced in the furnacefso that it is necessaryv to use about 50% more titanic anhydride than the desired increase of this compound Enough steel so that the total amount of iron in the charge shall, be at least three times the amount of silicon, in order to make the resulting ferrosilicon magnetic. Suflicient ulverized coke, or carbon in other form, is added,'so that with the carbon supplied by the wastage of the electrodes and furnace lining, part of the iron oxide and silica will be reduced at the temperature at which the furnace is operated. The amount of coke upon the quantity of silica and iron oxide present in the aluminous ore used. Not more than 3% each of silica and iron oxide must. be left unreduced. The different ingredients are thoroughly mixed before melt- %he melting operations may be performed in any suitable electric furnace. The charge is fed gradually into the furnace. When sufiicientmat'erial has been melted the mass is allowed to cool slowly to permit an annealing action to take place. We prefer to cool the product within the furnace at such a'rate that it will show redness 12 hours after the source ofheat has been discontinued.

,.The titaniferous ores above referred to, like other metallic ores, are impure oxides. Refined ores may be used as well in carrying out 'our method.

quantities of both'silica and iron We claim: F 1. in the manufacture of artificial corundum the improvement which consists in re ulating the percentage of titanic anhydri e in it to control the resistance to fracture and to adapt it to various grinding and polishingoperations while providing appreciable oxide in the product.

2. The herein described method ofcontrolling the resistance to fracture of artificial corundum which consists in regulating the percentagev of titanic anhydride in it by adding a titaniferous .oreto the furnace charge while providing appreciable quantities ofboth' silica and iron oxide in the product.

a. The. herein described method of conmenace trolling the resistance to fracture of artificial corundum which consists in regu ating the percentage of titanic anhydride in it by adding a compound of-titanium to the fur nace charge while providing appreciable quantities of both silica and iron oxide in the product.

4. The herein described method of controlling the resistance to fracture of artificial corundum which consists in adding to the furnace charge a sufficient quantity of titaniferous ore to produce the desired content of titanic anhydride in the product.

5. The herein described method of adjusting the resistance to fracture of artificial corundum, to the toughness of the material to be ground or polished, which consists in regulating the percentage of titanic anhydride in it, by addin ihnenite or other titaniferous ore to the rnace charge while silica and iron oxide in the product.

6. The herein described method which consists in adding a titaniferous ore to impure alumina containing silica and iron oxide, melting the mixture and artially re: ducing the silica and iron oxi e, the silica and iron oxide remaining in the product in aplgeciable quantities but to less than 3% eac i 7. The herein described furnace method providing appreciable 'quantities of both which consists in adding to impure alumina containing silica and iron oxide a suflicient l quantity of titaniferous ore' to produce a predetermined content of titanic anhydride in the finished product, melting the mixture and partially reducing with carbon the silica and iron oxide, the silica and iron oxide remaining in the product inappreciable quantities but to less than 3% each.-

8. The herein described furnace-method which consists in adding to impure alumina containing silica, iron oxide and titanic anhydride, a sufficient quantity of titanium compound to produce a predetermined content of titanic anhydride in the finished product, melting the mixture and partially reducin with carbon the silica and iron oxide, t e silica and iron oxide remaining in the product-in appreciable quantities but to less than 3% each.

9. The herein described furnace method which consists in adding a compound of titanium to f impure alumina containiiig silica, iron oxide and titanic anhydride, melting the mixture and partially reducing with carbon the silica and iron oxide, the silica and iron oxide remaining'in the prodnot in appreciable quantities but to less than v 3% each. i

10. The herein described furnace method which consists in adding a compound of titanium to impure alumina containingsilica, iron oxide and .titanic anhydride, melting the mixture, reducing in part the titanium compound and the silica and iron oxide, the silica and iron oxide remaining in the product in appreciable quantities but to less than 3% each.

11. The herein described furnace method which consists in adding ilmenite to impure alumina, melting the mixture, reducing in part the titanic anhydride and the other impurities, the silica and iron oxide remaining in the product in appreciable quantities but to less than 3% each.

12. A 116W composition of matter being an aluminous abrasive and consisting essentially of crystalline alumina containing more than 3% titanic anhydride and appreciable quantities but not. more than 3% each of the oxides of both iron and silicon.

13. As an abrasive artificially prepared crystalline alumina containing silica iron oxide and titanic anhydride in such proportions that grains measuring one-tenth of an inch across 'Will on the average sustain a pressure of more than 70 pounds without crushing.

r14. As an abrasive impure artificially pre pared crystalline alumina containing more than 3% titanic anhydride and not vexceeding 3% each silica and iron oxide, and Whose resistance to fracture is such that grains measuring one-tenth of an inch across will on the average sustain a pressure of more than 70 pounds.

HAROLD A. RICHMOND. ROBERT MACDONALD, JR. 

